NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Research Needs in Wind Energy

Natural Gas – The Path 

to Clean Energy Forum

November 18, 2010

Scott Schreck

NREL’s National Wind 

Technology Center

NREL/PR-5000-49975
National Renewable Energy Laboratory Innovation for Our Energy Future

Overview

• Genesis of 20% wind energy

• How much energy is 20%

• Is there enough wind to reach 20%

• Technology opportunities & challenges

2
A New Vision For Wind Energy in the U.S. 

State of the Union Address

“...We will invest more in ... 

revolutionary solar and wind 

technologies”

National Renewable Energy Laboratory Innovation for Our Energy Future

Advanced Energy Initiative

“Areas with good wind resources have the 

potential to supply up to 20% of the 

electricity consumption of the United States.”
National Renewable Energy Laboratory Innovation for Our Energy Future

Administration's Renewable Energy Goals

• Double renewable energy capacity by 2012

• 10% renewable energy by 2012

• 25% renewable energy by 2025

• Create 5 million new green jobs

• 80% GhG reduction (from 1990 levels) by 2050

• Informed by “20% wind energy by 2030” landmark report issued 

by DOE in May 2008

4
Electrical Power Generation by Source

Source: Electric Power Monthly, March 15, 2010 

http://www.eia.doe.gov/cneaf/electricity/epm/epm_sum.html

3700 TWh Annually

(0.42 TW Continuous energy use)
National Renewable Energy Laboratory Innovation for Our Energy Future

20% Requires 300 GW - Land & Offshore

0

50

100

150

200

250

300

2000 2006 2012 2018 2024 2030

Cumulative Installed Capacity (GW)

Offshore

Land-based

Actual

Projected
National Renewable Energy Laboratory Innovation for Our Energy Future

U.S. Wind Resource & Electrical Load
National Renewable Energy Laboratory Innovation for Our Energy Future

How Much Wind is Available ... Really?

Excludes PTC; includes transmission costs to access 10% existing electric 

transmission capacity within 500 miles of wind resource. Source: Black & Veatch/NREL

50% of US 

Electricity
Required Manufacturing Capacity

National Renewable Energy Laboratory Innovation for Our Energy Future

0

2

4

6

8

10

12

14

16

18

Annual GW Installed

Actual installations 

2007: 5,329 MW

Actual installations 

2008: 8,500 MW

Annual Installed Capacity (GW)

Capacity additions in 20% Scenario

AWEA 2009 Projections:

Additional Installed Capacity ≈ 10 GW

Total Installed Capacity ≈ 35 GW

Actual installations 

2009: 9,644 MW

2009: Wind was 47% of all New 

Domestic Power Generation 
National Renewable Energy Laboratory Innovation for Our Energy Future

Electric Sector CO2 Emissions

Cumulative

CO2 Savings

(2007-2050, MMTons)

Present Value Benefits

(billion 2006$)

Levelized Benefit of Wind

($/MWh-wind)

15,300 MMTCO2 50 - 98 - 145 9.7 - 19 - 28.2

CO2 regulation fees from Synapse (2006). $/ton CO2: Lo 10; Med 22; Hi 34.
National Renewable Energy Laboratory Innovation for Our Energy Future

Significant Water Use Savings 

0

2008 2010 2012 2014 2016 2018 2020

Year

2022 2024 2026 2028 2030

100

200

300

400

500

Billio

n

G

allo

n

s

S

a

v

e

d

Cumulatively, the 20% Wind Scenario would avoid the 

consumption of 4 trillion gallons of water through 2030

The 20% Wind Scenario cuts electric sector water 

consumption by 17% in 2030
National Renewable Energy Laboratory Innovation for Our Energy Future

Technology Evolution 

Credit: NREL Historical Photos
National Renewable Energy Laboratory Innovation for Our Energy Future

• 2.5 MW - typical commercial 

turbine Installation

• 5.0 MW prototypes being 

installed for testing in Europe

• Clipper Wind Power developing 

an 8.5 MW turbine

• Most manufacturers have a 10 

MW machine in design

• Large turbine development 

programs targeting offshore 

markets

• Development Outpacing Test & 

Validation Capability

Wind Turbine Scale – Present and Future

Boeing 747- 400

Clipper 2.5 MW, 99 m rotor

PIX #14647
Technology Opportunities

Power Conversion 

• High temperature silicon carbide 

device; improved reliability & 

reduce hardware volume

• Novel circuit topologies for high 

voltage & power quality 

improvement

• Medium voltage designs for 

multi-megawatt architectures

Tower Support Structures

• Tall tower & complex terrain deployment

• Advanced structures & foundations

• New materials and processes

• Self erecting designs Active Rectification

Inverter Bridge

(6 SiC MOSFETs and

6 SiC Schottky Diodes)

Inverter Bridge

(6 SiC MOSFETs and

6 SiC Schottky Diodes)

DC Bus

With Capacitors

Filter

Inductors

Input

(Generator)

Output

(690 VAC)

690 VAC

(Nominal)

3-Phase

Generator

 

Telescoping

Tower Jack Up Tower
National Renewable Energy Laboratory Innovation for Our Energy Future

Deep Water Wind Turbine Development

Current Technology
Advanced Rotor Technology 

• Extended rotor architectures through 

load control

• Incorporate advanced materials for 

hybrid blades

• Cyclic & independent blade pitch 

control for load mitigation

• Sweep and flap twist coupled 

architectures

• Light weight, high TSR with 

attenuated aeroacoustics

Power Train Enhancements

• Permanent Magnet DD 

Architectures

• Split load path multi-stage 

generation topologies

• Reduced stage (1-2) integrated 

gearbox designs

• Convoloid gearing for load 

distribution

Technology Opportunities
Current Activity:

NREL - Siemens 2.3 MW Aerodynamics Test

• Extensive pressure measurements

• LIDAR wake measurements

• Understand rotor / wake interaction

• CFD model validation

• Advanced aerodynamics / performance / loads 

control

Aeroacoustic array development – testing of 

Northwind, testing in Bushland with Sandia 

Planned/Recommended:

• Wakes – Comprehensive effort including CFD, 

wind tunnel test, field test; leading to improved 

design codes

• Acoustic testing of Siemens (array) – GE, 

CART3 – removable tip testing for noise

• “Siemens Part II”: wind farm 

atmosphere/turbulent inflow/aero/wake

Critical need for advanced wake models

Key to understanding array effects for 

performance & loads

Technology Opportunities

PIX 09996
National Renewable Energy Laboratory Innovation for Our Energy Future

Offshore COE Cost Breakdown

LRC & Lease 

Cost

6%

Electrical 

Infrastructure

12%

Eng/Permits 4%

Support Structure

14%

Misc BOS

13%

Offshore 

Warranty

6%

Turbine

32%

O&M (After 

Tax)

13%

Needs Improvement:

• Gearbox performance

• Operating expenses to high

• Capital expenses still exceed DOE 

performance goals

• Rotor stretching strategy

• Wind plants under-performing 10%

Why:

• Bearing failures; inaccurate 

internal loads?

• Unscheduled maintenance, low 

reliability, lack O&M automation

• Fatigue load & deflection control 

required

• Tower clearance limit, materials, 

aeroacoustics limiting tip speed, 

dynamic stability?

Serious Challenges Remain

Onshore COE Cost Breakdown

O&M (After Tax)

9%

LRC & Lease 

Cost

10%

Electrical 

Infrastructure

7%

Foundation

3% Misc BOS

11%

Turbine

60%

Existing design codes & tools 

should achieve 20 year life & 

reliable power performance 

predictions;

What are we missing?
19

: Axial velocity : Turbulence intensity

Near wake ? Far wake

Sørensen, EWEC 2007

Wake Structure Development
Turbine, wind farm, PBL; 

similar dimensional scales 

Farm / inflow interactions not 

quantified

Characterization & prediction 

remain an issue

Detailed inflow information 

required for turbine design and 

optimized control 

Diurnal variation

Growing concerns include:

– Quality of the downwind 

resource

– Microclimatology changes

– Agriculture impacts

– Permitting

20

sunset

midnight

Planetary Boundary Layer (PBL)
National Renewable Energy Laboratory Innovation for Our Energy Future

DOE 1.5 MW GE Turbine:

• Model: GE 1.5SLE

• Tower Height: 80 m

• Rotor Diameter: 77 m

• DOE owned; used for research and 

education

Siemens 2.3 MW Turbine:

• Model: SWT-2.3-101

• Tower Height: 80 m

• Rotor Diameter: 101 m

• Siemens owned and operated

• Multi-year R&D CRADA; aerodynamics 

and rotor performance

Multi-MW Turbines at NWTC

DOE 1.5 MW

Siemens 2.3 MW

PIX #17694

PIX #17720
Large Facility Requirements

A 45-meter wind turbine blade 

undergoing fatigue testing at the 

NWTC, July 2004.

National Renewable Energy Laboratory Innovation for Our Energy Future

New Large Blade Test Facility

• Boston, MA with Massachusetts 

Technology Collaborative 

New Dynamometer Test Facility

• Charleston, SC with Clemson 

University

PIX #12414

PIX #13889
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Scott Schreck

National Wind Technology Center

Phone: +1 (303) 384-7102

Email: scott.schreck@nrel.gov

Questions?

PIX 17245